Navigational marker



Aug. 20, 1968 c. G. HOUTSMA NAVIGATIONAL MARKER Filed Oct. 25, 1966 CORNELIUS 6. HOUTSMA ATTORNEY United States Patent 3,397,413 NAVIGATIONAL MARKER Cornelius G. Houtsma, Winchester, Mass. United States Coast Guard, First Coast Guard District, John F. Kennedy Federal Bldg., Government Center, Boston,

Mass. 02203) Filed Oct. 25, 1966, Ser. No. 589,470 4 Claims. (Cl. 9-8) ABSTRACT OF THE DISCLOSURE The present invention provides a unique and novel navigational marker which will maintain an upright position in slack water or in a moving current. A typical embodiment comprises a flotation member of foamed plastic, which may incorporate a radar reflector, and a concrete ballast in the form of a spherical segment. Balancing of the horizontal current forces is achieved by attaching the mooring line at a point on the submerged portion of the marker such that the area above that point is equal to the area below that point. Vertical stability is provided by the downward force created as a result of the different water flows on the upper and undersides of the ballast.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This invention relates to marine navigation and more particularly to a lightweight navigational marker which is highly stable in still or moving water.

Navigational markers or buoys are extensively used to locate channels or obstructions in rivers or in sea approaches to ports and harbors. Channels, in particular, are delineated by nun buoys, i.e., truncated cones, and by can buoys, i.e., right circular cylinders. Previous to the present invention, most navigational markers when subject to changes in the current become difficult to correctly identify because they lean in response to the current, that is to say, their vertical axes do not remain perpendicular to the surface of the water. Furthermore, buoys of conventional design are usually moored so that they must lean in a slow current and often submerge completely in a fast current. Under such conditions, the buoy becomes invisible, or a leaning can buoy may easily be mistaken for a nun buoy. Further, previous navigational markers when designed to remain upright in a current failed to do so in still water. Such navigational markers are practically useless under tidal conditions where the current varies from zero velocity to several knots.

The general purpose of this invention is to provide a. navigational marker which will remain upright in still or moving water. This is attained in the navigational marker of the present invention by proportioning of the underwater elements of the navigational marker so that in still water all forces acting about the anchoring point are balanced. In addition, this proportioning feature is combined with a uniquely designed ballast element which exerts a downwardly acting stabilizing force in moving water, directly responsive to the current strength. A typical embodiment of this invention comprises a lightweight, foamed plastic flotation assembly either in the shape of a truncated cone (nun) or in the shape of a right circular cylinder (can), and a support assembly including a ballast element of reinforced concrete or other suitable dense material in the form of a spherical segment. Further, integral radar reflectors can be incorporated within the flotation assembly. Because the navigational marker of the present invention is highly stable, visual recognition is improved and directional radar reflectivity remains constant.

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It is an object of this invention to provide a navigational marker which is stable and which remains upright in still or moving water.

Another object of this invention is the provision of a navigational marker having underwater elements so proportioned that all forces about the anchoring point are balanced.

A further object of this invention is to provide a ballast element for a navigational marker which stabilizes the navigational marker in moving water by producing downwardly acting stabilizing force proportional to the current.

Still another object of this invention is the provision of a navigational marker which is readily distingugishable and which maintains a constant directional radar reflectivity.

Yet another object of this invention is to provide a lightweight, durable, navigational marker which is simply constructed and easily handled by a small boat.

The exact nature of this invention, as well as other objects and advantages thereof, will be readily apparent from consideration of the following specification relating to the annexed drawings in which:

FIGURE 1 shows a side elevation, in section, of a navigational marker made in accordance with this invention in its operating environment, and

FIGURE 2 is an exploded perspective view of the flotation assembly of FIGURE 1, illustrating the placement of the radar corner reflectors.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIGURE 1 a navigational marker of this invention wherein 10 is the surface of the water in which the marker is anchored. The navigational marker consists of a flotation assembly generally denoted by the numeral 12 and a support assembly generally denoted by the numeral 14. The support assembly 14 includes a base plate 16 on the upper surface of which is rigidly mounted a rod 18 by means of a spider 20. Rod 18 is threaded on its upper end to facilitate the attachment of the flotation assembly. A tube 22 is also attached transversely to the upper surface of the base plate 16. By means of a bolt 24 and a nut 26 inserted in tube 22 fastening bail 28 is rotatably or pivotably connected to the support assembly. Plastic or other bearing material may be utilized to reduce friction between the bolt 24 and the tube 22. A spreader 30 may be used to reinforce the fastening bail. On the undersurface of base plate 16, studs 32 are rigidly attached as, for example, by means of flanges 34. Ballast 36 is coupled to the studs 32 by means of angled lugs 38 and unions 40, the lower, protruding ends of studs 32 being threaded for this purpose. Unions 40 are provided so that the ballast 36 may be easily removed for cleaning. The ballast 36 is formed so that its lower surface is convex with respect to its upper surface, and it may be constructed of reinforced concrete.

The navigational marker is anchored by line 42 drawn through eyelet 44 on fastening bail 28 and shackled to chain 46 and sinker 48. To absorb shocks, line 42 is purposely made relatively elastic, e.g., conventional nylon rope may be used. Additional secondary sinkers 50 may also be utilized and are slideably linked to the chain 46 by means of tail chains 52 and rings 54. In use, the secondary sinkers do not fall to the extreme end of chain 46, but remain spread out along this chain. Thus, chain 46 becomes flattened and parallel to the bottom. An exceedingly heavy strain on the navigational marker causes the sec ondary sinkers to place a tension on chain 46 before primary sinker 48 is given an upward lifting component, thus, introducing a forced catenary and enabling a lighter weight to exert a better holding power.

The flotation assembly 12 includes a buoyant member 60 and integral radar corner reflectors 62, one reflector being shown in phantom. Buoyant member 60 is fabricated from a low density, cellular, foamed plastic, such as Styrofoam, covered with one or more layers of fiberglass reinforced plastic resin 64. The buoyant member may be formed as a cylinder, i.e., a can buoy, or as a truncated cone, i.e., a nun buoy, shown in dotted lines as 65 in FIG- URE l. The flotation assembly includes a centrally located bore 66, a recess 68, and a slot 70 dimensioned so as to fit snugly over rod 18, spider 20 and tube 22. The flotation assembly is attached to the support assembly 14 by means of cover plate 72 and eyebolt 74. Because the navigational marker of this invention is of relatively light weight construction, it may easily be lifted by eyebolt 74 by a small boat without the use of a crane or mechanical hoisting equipment. Before assembly the metal parts of the support assembly are preferably coated with a plastic corrosion inhibitor.

The radar reflector 62 is constructed of thin sheet aluminum or other light metal or copper screen wire and is preferably in the form of a corner reflector having three mutually perpendicular faces. Several radar reflectors may be incorporated into the buoyant member to provide omnidirectional radar reflectivity. They may be formed in place by conventional foaming techniques during the molding of the buoyant member or installed subsequently in the manner illustrated in FIGURE 2.

In FIGURE 2, a cylinder buoyant member 60 with a sector 76 removed is shown. A radar corner reflector 62 is cemented in place and thereafter sector 76 is split or slotted and replaced permanently in its original position as shown at 78. After the desired number of reflectors are added, the entire outside surface of a buoyant member is encased in fiberglass reinforced plastic resin 64.

The navigational marker constructed in accordance with this invention is so proportioned that when resting in still water the projected area of the marker under the surface of the water above the anchoring point, i.e., the tube 22, is equal to the projected area of the ballast 36 and its associated fittings below the anchoring point. By projected area is meant the lateral area which is seen when the marker is viewed in any direction perpendicular to its vertical axis. This area is the same in any direction since the vertical axis is a rotational axis of infinite symmetry. Thus, the navigational marker of this invention has no unbalanced component of force to make it tilt out of the vertical. If the navigationalmarker is anchored in a current stream, the dependent, spaced apart relationship of the ballast to the base plate permits water to flow over both the upper and under surfaces of the ballast. However, because the water must flow more rapidly over the convex undersurface of the ballast, a reduced pressure is created on the undersurface of the ballast causing the buoy to sink until the forces acting on the marker again equalize. The action of the increased water flow over convex under surface of the ballast is analogous to the aerodynamic lift produced by air flow over an aircraft wing structure. Because the forces acting on the navigational marker are at all times balanced, there is little to prevent oscillation of the marker around the pivot point of the bail if a discontinuity exists in the current stream. But the reaction of the uniquely designed ballast of this invention quickly damps such oscillations. Thus, the navigational marker of this invention remains stable and upright in calm or swift water. Visible detection of the marker is enhanced and the directional reflectivity of the marker to radar remains constant.

The navigational marker of the present invention is characterized by the proportioning of the underwater elements of the marker so that the force acting about the anchoring point are balanced in still water. It is further characterized by an uniquely designed ballast which produces a downwardly acting stabilizing force in moving I water. A typical embodiment of this invention includes a low density, cellular, foamed, plastic buoyant member and a reinforced concrete ballast in the form of a spherical segment. Such a navigational marker remains stable and upright in calm or swift Water and, thus, useful to the mariner when others are submerged or unrecognizable. The navigational marker of this invention will remain upright with any speed of current and becomes increasingly stable as the current speed increases. Further, it is lightweight, durable, readily constructed and easily handled. Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Having thus described the invention, what is claimed is:

1. A navigational marker comprising a flotation assembly, a support assembly, said flotation assembly being attached to said support assembly, said support assembly including anchoring means attached at an anchoring point and dependent, spaced apart, ballast means having a lower surface convex with respect to its substantially flat upper surface, and said flotation assembly and said support assembly being proportioned so that in still water the lateral projected underwater area of the navigational marker above the anchoring point is equal to the lateral projected underwater area below the anchoring point and said convex lower surface and substantially flat upper surface of the ballast producing a downwardly acting stabilizing force caused by the flow of moving Water around said surfaces.

2. A navigational marker in accordance with claim 1 wherein the flotation assembly includes a buoyant member of low density, cellular, foamed plastic.

3. A navigational marker in accordance with claim 2 wherein the buoyant member has incorporated therein at least one corner radar reflector.

4. A navigational marker comprising a flotation assembly including a buoyant member of low density, cellular, foamed plastic, at least one radar corner reflector incorporated within said buoyant means, the external surfaces of said buoyant member being covered with fiberglass reinforced plastic resin, a support assembly including, a base plate, an upwardly extending rod mounted on said base plate and adapted for attaching said flotation assembly to said support assembly, a tube transversely attached to said plate, a bolt rotatably inserted in said tube, said bolt having attached thereto a fastening bail, downwardly extending studs attached to said base plate, and ballast removably coupled to said studs in spaced apart, dependent relationship to said base plate, said ballast having a lower surface convex with respect to its upper surface, said flotation assembly and support assembly being proportioned so that in still water the projected area of the support assembly and flotation assembly below the surface of the water and above the transversely attached tube is equal to the projected area of the support assembly and flotation assembly below the surface of the water and below the transversely attached tube, and said convex lower surface of said ballast producing a downwardly acting stabilizing force in moving water.

References Cited UNITED STATES PATENTS 1,974,832 9/1934 Peterson 98.3 X 2,119,697 6/1938 Anderson 98.3 X 2,716,758 9/ 1955 Hajecate 98 3,176,644 4/1965 Thomas et al. 114-126 MILTON BUCHLER, Primary Examiner.

T. MAJOR, Assistant Examiner. 

